The present invention relates generally to nonwoven, natural-fiber fabrics, and specifically to a nonwoven fabric of hydrodynamically entangled waste cotton fibers, which fabric is suited to form, among other things, bags for containing cotton bales.
Cotton fiber, a so-called xe2x80x9cnatural fiberxe2x80x9d because it is taken from a plant instead of from a synthetic source such as petrochemicals, is widely used in making fabrics of various types. Before cotton can be used as a fabric, it must undergo a series of processing steps. The cotton plant produces bolls of raw cotton, which are typically mechanically harvested and delivered to a gin, where foreign material such as dirt, plant matter, and insect parts are removed, and where the fiber is separated from the seeds embedded within it.
The cotton fiber then undergoes successive processes, such as picking and combing, to clean the fiber further and to cause the individual fibers to begin to cohere, or align. Picked cotton fiber destined to become yarn for weaving or knitting is then laid down into a lap. Carding further refines the cotton fiber and begins the process of removing short-staple fibers, which are considered to be too short to be commercially useful in a yarn. Longer fibers generally provide greater resistance to breaking (in a yarn) or tearing (in a woven or knitted fabric). Short-staple, or xe2x80x9cwaste cotton,xe2x80x9d fibers have typically been regarded as not usable in yams and fabrics, and so have been used only for their absorptive capabilities, rather than for their tensile strength, in disposable products such as diapers, sanitary napkins, cigarette filters, and the like.
Because ginned cotton is fairly lightweight, it is useful to compress it into bales of a convenient size for transportation. Once cotton has been compressed, however, it is necessary to hold it in a compressed condition. Historically, this was accomplished by placing bands around the bale and wrapping the bale in burlap or in a woven or knitted fabric. A more modern method is to wrap the bale in polyethylene film or in woven polypropylene, typically in a bag form, after banding. Wrapping the bale also keeps dirt and foreign matter from contaminating the ginned cotton. Though covering the bale is a necessary step, these coverings create an additional expense for the cotton processor. Consequently, it is desirable to use a material that may be obtained inexpensively, in order to reduce processing costs.
Briefly summarized, the present invention provides for a non-woven fabric comprises hydrodynamically entangled waste cotton fibers to form a binderless integrated web. Hydrodynamic entanglement, also known as hydroentanglement or hydroneedling, is a process that is well known in the art of textile manufacturing. Hydrodynamic entanglement is usually accomplished by feeding a thick batt of fibers through a series of fine jets of water at water pressures ranging from 10 to 600 bar or more. Energy transferred from the jets of water serves to compact or punch down the batt of fibers, to cause the fibers to cohere, and to entangle the fibers. Often, and especially in the case of natural fibers, a thermoplastic material is intermixed with the fibers to enable them to be thermally bonded, thereby increasing the strength of the fabric. The end result is a non-woven fabric of a fairly uniform density and strength. Hydrodynamic entanglement is typically used to entangle so-called xe2x80x9cendlessxe2x80x9d fibersxe2x80x94for instance, synthetic fibers that are extruded from molten plastic and have a far greater fiber length than natural fibers. One common use for hydroentangled fiber fabrics is for surgical gowns and drapes; because of the relatively inexpensive manufacturing process, such fabrics are disposable and thus ideal for such xe2x80x9csingle-usexe2x80x9d applications.
Although hydrodynamic entanglement is well known for synthetic fibers and usable for long-staple natural fibers, heretofore the process has not been used to process waste cotton fibers into usable fabric, nor has the process been thought to be capable of effectively forming usable fabric from waste cotton fibers. An object of the present invention is, therefore, to provide for a fabric comprising waste cotton fibers that have been hydrodynamically entangled. As used herein, the term xe2x80x9cwaste cotton fibersxe2x80x9d is intended to mean cotton fibers predominantly of a staple fiber length less than about 1xe2x85x9 inches, which are primarily unsuitable for spinning into a usable yarn, although longer fibers may be used without departing from the scope of the invention.
It is another object of the present invention to provide for a fabric that does not require a thermoplastic bonding agent in order to form an integrated web of waste cotton fibers, because of the expense associated with providing and interspersing such an agent within the batt.
It is still another object of the present invention to provide for a bag, suitable for containing and protecting a bulk materialxe2x80x94such as ginned and baled cottonxe2x80x94which is formed from fabric comprising a binderless cohesively integrated web of hydrodynamically entangled waste cotton fibers, and which may be provided at a substantially smaller cost than traditional bags.
It is a further object of the present invention to provide for the combination of a cotton bale and a cover for the bale, the cover comprising a fabric that includes a cohesively integrated web of hydrodynamically entangled waste cotton fibers.